// Copyright 2016 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef CC_TREES_ELEMENT_ID_H_
#define CC_TREES_ELEMENT_ID_H_

#include <stddef.h>

#include <cstdint>
#include <functional>
#include <iosfwd>
#include <memory>

#include "base/hash.h"
#include "cc/base/cc_export.h"

namespace base {
class Value;
namespace trace_event {
    class TracedValue;
} // namespace trace_event
} // namespace base

namespace cc {

// An "element" is really an animation target. It retains the name element to be
// symmetric with ElementAnimations and blink::ElementAnimations, but is not
// in fact tied to the notion of a blink element. It is also not associated with
// the notion of a Layer. Ultimately, these ids will be used to look up the
// property tree node associated with the given animation.
//
// These ids are chosen by cc's clients to permit the destruction and
// restoration of cc entities (when visuals are hidden and shown) but maintain
// stable identifiers. There will be a single layer for an ElementId, but
// not every layer will have an id.
struct CC_EXPORT ElementId {
    ElementId(int primaryId, int secondaryId)
        : primaryId(primaryId)
        , secondaryId(secondaryId)
    {
    }
    ElementId()
        : ElementId(0, 0)
    {
    }

    bool operator==(const ElementId& o) const;
    bool operator!=(const ElementId& o) const;
    bool operator<(const ElementId& o) const;

    // An ElementId's conversion to a boolean value depends only on its primaryId.
    explicit operator bool() const;

    void AddToTracedValue(base::trace_event::TracedValue* res) const;
    std::unique_ptr<base::Value> AsValue() const;

    // The compositor treats this as an opaque handle and should not know how to
    // interpret these bits. Non-blink cc clients typically operate in terms of
    // layers and may set this value to match the client's layer id.
    int primaryId;
    int secondaryId;
};

CC_EXPORT ElementId LayerIdToElementIdForTesting(int layer_id);

struct CC_EXPORT ElementIdHash {
    size_t operator()(ElementId key) const;
};

// Stream operator so ElementId can be used in assertion statements.
CC_EXPORT std::ostream& operator<<(std::ostream& out, const ElementId& id);

} // namespace cc

#endif // CC_TREES_ELEMENT_ID_H_
